When using the UART (RS-232 Serial Port) why is my baud rate incorrect? - When using the UART (RS-232 Serial Port) why is my baud rate incorrect? Description You may experience this problem when using the UART (RS-232 Serial Port) component in a Qsys design with Quartus® II software version 11.0. This may result in the UART not synchronizing or communicating with the other end. To work around this issue calculate the correct divisor_constant, by dividing the UART input clock frequency assigned to the UART, by the assigned Baud rate(bps), then verify this value is assigned to the divor_constant simulation varible in the Qsys generated <Qsys_system_name>_uart_0 file. If needed change the assigned value to match your calculation. For example, the input clock to the Qsys UART is 83MHz. The assigned Baud rate(bps) = 115200. The divisor should be 83,000,000 / 115200 = 720. When verifying this value in the _uart_0 file you find the following lines of code: //synthesis translate_on //synthesis read_comments_as_HDL on // assign divisor_constant = 434; //synthesis read_comments_as_HDL off Change the divor_constant = 720 as shown below. // assign divisor_constant = 720; This problem is fixed in Quartus II software version 11.0 SP1. Custom Fields values: ['novalue'] Troubleshooting novalue False ['novalue'] ['FPGA Dev Tools Quartus II Software'] 11.0.1 11.0 ['Programmable Logic Devices'] ['novalue'] ['novalue'] ['novalue']